Incomplete 5 - Plasma Membranes Flashcards
What do channel proteins do?
Provide a pathway for diffusion (passive)
What do carrier proteins do?
Move molecules against the concentration gradient
What do glycolipids do?
acts as a recognition site cell markers (recognised by antigens as self-cells)
What do glycoproteins do?
- cell adhesion
- receptors for chemical signals
What are extrinsic proteins?
-proteins present on one side of the bilayer
What are intrinsic proteins? Give 3 examples
sit permanently within the membrane
- channel proteins
- carrier proteins
- glycoproteins
Explain the differences in how hydrophilic and hydrophobic molecules pass through membranes
HYDROPHOBIC
- can pass straight through bilayer
- rapid
HYDROPHILLIC
- repelled by hydrophobic core of bilayer
- have to pass through pores
- more slowly
State 3 functions of plasma membranes
1-site of chemical reactions
2-partially permeable membrane
3-cell communication
Define compartementalisation
Separation of different areas allowing for different, often incompatible, reactions
What is the role of cholesterol in plasma membranes?
increases the stability of the membrane (without making it too rigid)
Describe how temperature affects membrane structure
- -increases in temperature causes increase in KE
- -therefore the membrane becomes more disrupted and more permeable
- -(could eventually be destroyed)
Describe how solvents affect membrane structure
- -molecules can pass into but not through the bilayer and disrupts fluidity
- -increases the permeability
- -(could eventually be destroyed)
State 6 factors the affect diffusion
- -diffusion pathway (distance)
- -surface area
- -temperature
- -size of molecule
- -conc. gradients
- -the thickness of cells through which they dissolve
Describe how temperature affects rate of diffusion
Increases KE and more frequent collisions
Describe how distance of diffusion pathway affects rate of diffusion
Molecules lose energy with each collision, longer distances need more KE
Describe how surface area affects rate of diffusion
High area = more opportunities for molecules to pass through
Describe how size of molecule affects rate of diffusion
bigger molecule means more energy needed to move molecule
What is facilitated diffusion?
Passive process but involves channel proteins for when molecules can not pass through membrane (eg. ions)
What makes active transport different to diffusion
Not passive, against a conc. gradient, selective
What features of the plasma membrane are used in active transport
Cells use specific carrier proteins to pump substances across the membrane
